Rheostat



May 2, 1944.

c. F. LEATHERS 2,347,695

RHEOSTAT Filed Feb. 25, 1942 3 ShsetsSheet I5 08 ,wz /aa ATTOR a Patented May 2, 1944 UNITED RHEOSTAT Chester F. Leathers, Detroit, Mich, assignor to Progressive Welder Company, Detroit, Mich, a

corporation of Michigan Application February 25, 1942, Serial'No. 432,194

2 Claims.

The present invention relates to rheostats.

Principal objects of the present invention are to provide an improved electrical contactor arranged toopen and close a circuit and further incorporating means to introduce resistance into the circuit at the beginning of each closing operation and to progressively decrease such resistance during the course of each closing operation; to provide such a contactor operable to progressively re-introduce said resistance into the circuit during the course of each opening movement; to provide such a contactor incorporating movable and stationary contact elements, resistance elements, and further arranged to provide a rolling contact between said elements; and to provide such a contactor which may be readily and economically manufactured and which is capable, though of relatively small size, to handle extremely large current values.

With the above as well as other objects in view, which appear in the following description and in the appended claims, a preferred but illustrative embodiment of the invention is shown in the accompanying drawings, throughout the several views of which corresponding reference characters are used to designate corresponding'parts and in which:

Fig. 1 is a view in front elevation of a contactor embodying the invention;

Fig. 2 is a fragmentary view, taken along the line 2'-2'of Fig. 1;

Fig. 3 is a view in horizontal section, taken along the line 3-3 of Fig. 1;

Fig. 4 is a view in horizontal section, taken along the line 4-4 of Fig. 1;

Fig. 5 is a view in vertical section, taken along the line 55 of Fig. 3;

Fig. 6 is a view in vertical section, taken along the line 6-45 of Fig. 5; and

Fig. '7 is a view in vertical section, taken along the line 11 of Fig. 5.

The illustrated contactor comprises a lower grid member 22 and an upper grid member 24', shown in Figs. 1, 3 and 4, which are superimposed upon each other and which are arranged to have relative rolling contact with each other. In the normal or off position of the contactor, shown in Fig. 1, the insulating block 26 of the upper grid member bears upon the corresponding insulating blocks 28 of the lower grid member and the conducting elements of the two grid members are out of contact with each other, so that the circuit through the contactor is interrupted;

The insulating block 26 is connected to a conducting bar 3% through a pair of similar resistance grids 32. The insulating block 28 are connected to corresponding conducting terminals 34 by means of resistance grids 36. When th contactor is in its fully closed position, the bar 3! bridges the terminals 34, to which the external circuit may be connected. For intermediate po sitions of the contactor, the grids 32 rest, with a rolling contact, upon the-grids 36, thereby introducing into the associated circuit an amount of all of the grids 32 and 36 which is determined by the position of the contactor. For example, if the contactor is rocked counterclockwise from the open position of Fig. 1 to a position in which the points a of grids 32 rest upon points I) of grids 36, the circuit through the contactor is as follows:

From one terminal 34, the corresponding grid 36 to the point b thereof, the co-operating upper grid 32 from the point a thereof to bar 30, the other grid 32 to the point a thereof, and the remaining grid 36 from point b thereof to the other terminal 34. As the contactor C is rocked further in a counterclockwise direction from the position of Fig. 1, the co-engaging points a and b of the grids 32 andtfi are advanced to the left, as viewed in Fig. 1, thereby progressively reducing the resistance in the circuit. When. the fully closed position is reached, the bar 30 directly engages the terminals 34, short circuiting the grids. During an opening operation, the opposite effect is obtained, the initial rocking movement of the contactor serving to introduce a minimum amount of the resistance grids and further such rocking movement progressively increasing the amount of such resistance until such time as the circuit is opened by the seating of the insulating blocks 26 and 23 upon each other. It will be appreciated that widely varying amounts of resistance can be introduced into, and excluded from, the circuit in the above described manner.

In the illustrated embodiment, the movement of the upper grid member relative to the lower grid member is controlled by a closing ram 40 and an opening ram t2, the supply and exhaust lines whereof may be controlled in any suitable manner. It will be appreciated that in the off position of the contactor, ram 42 is connected to the supply source and ram 49 is connected to exhaust. In the opposite or on position of the contactor, ram 4%] is connected to the supply source and ram @2 is connected to exhaust. The rams 40 and 42 are provided with conventional pistons, the piston rods whereof are coupled to the upper grid member in such relation as to provide the aforesaid operating relationship.

The illustrated construction comprises a rectangular plate-like base member 80 and upwardly extending end members 82 and 84. The end members may be and preferably are welded to the base member 00. The end members 82 and 84 are similarly formed and each comprises a base portion 86 having outwardly extending flange portions 88 and 90 at the sides, top, and bottom thereof. The upper flat surfaces of the end members 82 and 84 form seats to which the yokes 92 and 94 are secured, as by means of bolts 96. The upper ends of the Yokes 92 and 94 are inwardly turned, and provide clevises within which the rams 40 and 42 are pivotally secured by means of pins 98. The piston rods I and I02 of the rams 40 and 42, respectively, are pivotally connected by means of pins I04 and I06 to pairs of laterally spaced bearing blocks I08 and I I 0, which are secured to the upper grid member 24 at the opposite ends thereof.

The end member 82 also carries a pair of laterally spaced inwardly projecting bracket arms II2 which are provided with two spaced resilient bumpers II4 which are disposed to co-operate with the arm members II6 which are secured to and project upwardly from the upper grid 24. The bumpers H4 and the arms H6 co-operate as hereinafter described to cushion the final closing movements of the contactor.

More particularly, the bumpers II4 are secured at opposite ends of a bar II8, which is secured to a pin I20. The pin I20 projects loosely through an opening in a co-operating bar I22, and a spring I24 is provided to continuously urge the bar II8 towards the bar I22, which movement is limited by the adjusting screws I26, which are threadably received in the bar I22 and bear against the bar I I8. The spring I24 thus acts to withdraw the bar III! to whatever position of adjustment is determined by the screws I26. The bar I22 is rigidly secured to the previously-mentioned, spaced, forwardly projecting bracket members H2.

The lower grid member 22 comprises a pair of similar laterally spaced base members I 30, which are secured to the previously-mentioned base 80 by a plurality of studs such as I32, the heads whereof are loosely received in counterbored openings provided therefor in the base 80, and which studs are tightened down sufficiently to compress a bumper pad I34, formed of rubber or the like. The bumper pad is directly interposed between the base members 80 and I30, and, as will be evident, serves to cushion loads applied to the lower grid member 22 by means of the upper grid member 24.

The previously-mentioned lower grids 36 are of usual serpentine form and, like grids 32, may be formed of any of the usual relatively highly resistant material such as cast iron. The individual convolutions of the grids 35 are provided with mounting tabs I40 by which the grids are rigidly secured to a pair of supporting blocks I42 and I44, one pair of such blocks being individual to each grid 36. The right-hand end. of each base member I30 has a supplemental base member I48 rigidly secured to it as by welding, and these members I48 carry additional blocks I46, which carry carbon contact elements I50. The carbon con.- tact elements are held in place on the blocks I46 by clamps I52. The several pairs of blocks I 42, I44 and I46 may be formed of any suitable insulating material such as hard fiber. Blocks I42 (all and I 44 are rigidly secured to the corresponding base members I30 by studs such as I54.

The previously-mentioned conducting terminals 34 are secured by studs I60 to downwardly projecting portions I62 at the left-hand ends of the corresponding grid elements 36, and rest upon insulating plates I64, which, in turn, rest upon the corresponding base members I30. It will be noticed, accordingly, that the terminals 34 are connected to the base members I30 through the grid elements 36 and the fiber blocks I 42 and I44. The previously-mentioned insulating members 28 are connected, by means of studs I66, to the corresponding fiber blocks I46. It will be recalled that the blocks I46 are rigidly connected to the carbon contacts I50, and contacts I50, in turn, are rigidly connected to the grids 36. The assemblies comprising the blocks 28 and I46 and the carbon contacts I50 are, consequently, secured to the base I30 through the grids 36 and the blocks I42 and I44.

The upper grid member 24 is provided with a pair of laterally spaced base members I10 to which the previously-mentioned conducting terminal 30 and the insulating bar 26 are secured by means of studs I14 and I16. The upper grids 32 are also of serpentine form with the central convolutions therein arranged in vertical registry with the central convolutions in the lower grids 32. The upper grids are secured to a corresponding series of insulating blocks I80, I82 and I84, by means of screws I86, and these blocks, in turn, are secured to the base members I10 by means of studs I88. 32 are provided with upwardly turned flanges 32a, by which these grids are rigidly connected to the conducting terminal 30. The right-hand ends of the grids 32 are seated in and secured to corresponding carbon contacts I 90, which are complemental to the previously-mentioned carbon contacts I 50. The carbon contacts I are secured, by means of clips I92, to fiber blocks I94, which, in turn, are rigidly secured to the insulating member 26 by studs I98.

The main base member 80 is provided with two pairs of side plates 200 which project upwardly therefrom and define a cradle within which the upper grid member 24 is received. These plates, as will be understood, prevent movement of the upper grid member 24 laterally of the lower grid member 22. Corresponding guiding to keep the upper and lower grid members properly aligned with each. other lengthwise thereof is afforded in part by the rams 40 and 42, and in part by an articulated spring plunger 202, having an upper section 202a and a lower section 20217 pivoted thereto. The spring arm 202 passes downwardly between the laterally spaced halves of the upper and lower grid members and is provided with a compression spring 204 which acts between the arm 202 and a seat provided by an angle bracket 206 which extends between and is connected to the previously-mentioned upwardly projecting arms II6. It will be noticed that the spring 202 continuously urges the upper grid member to an intermediate position in which the upper and lower grids 32 and 36 engage each other at the longitudinally central points thereof, which biasing effect is, however, overcome by the forces applied to the upper grid member by means of the rams 40 and 42. It is preferred to supplement this aligning action by providing the upper grid member 24 with outwardly projecting pins I which ride in arcuate slots I91 formed in brackets I99 which are secured to the lower grid member The left-hand ends of the upper grids 22. It will be understood that the slot 191 is shaped to define the free path followed by pins I95 during the rocking movements of the contactor.

It will be noticed that the upper surfaces of the lower grids 3B, the terminals 34, the carbon blocks I50, and the insulating blocks 28 are formed as arcs of circles of equal radius and that the same is true of the under surfaces of the corresponding elements of the upper grid member 24. However, the radius of curvature of the upper grid member is somewhat smaller than the radius of curvature of the lower grid member, enabling the upper grid member to have rolling contact with the lower grid member in moving from the off position to the on position and vice versa.

It will be recalled from previous description that when the contactor is in the initial on posi- 7 tion, the circuit extends through all of the upper and lower grids in series relation with each other, and it will be noticed also that each upper grid 36 and the corresponding lower grid 32 together form a pair of grids. The present structure utilizes two such pairs of grids, but it will be understood that additional such pairs may be used, if desired. By the addition of further pairs of grids 3236 and co-operating contact elements, consequently, the number of grids available to the circuit may be increased at will.

Although only a single specific embodiment of the invention has been described in detail, it

will be appreciated, as aforesaid, that various changes may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In a contactor mechanism, the combination of a relatively fixed contact member having arcuately arranged portions, respectively, of low resistance, high resistance, and of insulating character, a relatively movable contact member having corresponding portions arranged on an arc of smaller radius, and means for rocking said relatively movable contact member from a position in which said insulating portions are in engagement through a position in which said high resistance portions are in engagement to a position in which said low resistance portions are in engagement.

2. In a contactor mechanism, the combination of a relatively fixed contact member having successively arranged portions, respectively, of low resistance, high resistance, and of insulating character, a relatively movable contact member having successively arranged corresponding portions, and means for moving said movable contact member from a position in which said insulating portions are in engagement through a position in which said high resistance portions are in engagement to a position in which said low resist ance portionsare in engagement.

CHESTER F. LEATHERS. 

